1. Field of the Invention
The present invention relates to surface acoustic wave devices each including a substrate, a support member, and a cover member and in which a hollow space is provided.
2. Description of the Related Art
Surface acoustic wave devices such as a resonator, a bandpass filter, and the like have been widely used. In order to miniaturize surface acoustic wave devices, a wafer level packaging technique has been making substantial progress these days. For example, Japanese Unexamined Patent Application Publication No. 2011-172190 discloses a surface acoustic wave device using the wafer level packaging technique.
In the surface acoustic wave device disclosed in Japanese Unexamined Patent Application Publication No. 2011-172190, an interdigital transducer (IDT) electrode and a wiring electrode are formed on a piezoelectric substrate. A support member is formed on the piezoelectric substrate so as to surround the IDT electrode, the wiring electrode, and the like. Further, an upper opening of the support member is sealed with a lid member, whereby a sealed hollow space is provided in the device. In order to miniaturize the device, a three-dimensional crossing section where one wire and the other wire cross each other via an insulation film is provided in the wiring electrode. Japanese Unexamined Patent Application Publication No. 2011-172190 discloses that the insulation film of the three-dimensional crossing section is formed of polyimide. Meanwhile, the support member is formed of a resin which is different from polyimide.
International Publication No. WO/2009/116222 and International Publication No. WO/2011/087018 each disclose a surface acoustic wave device such that a material forming an insulation film that is provided in a three-dimensional crossing section of a wiring electrode and a material forming a support member are different from each other. In addition, a structure such that the support member is not disposed above the three-dimensional crossing section is disclosed.
The following may be a reason why an insulation film used in a three-dimensional crossing section and an insulation film used in a support member are formed of different resins from each other in the conventional devices.
A thickness of the insulation film in the three-dimensional crossing section is approximately 1 μm to 3 μm in general. Meanwhile, to form a hollow space structure, a thickness of the support member is relatively large to be no less than 10 μm. As such, it has been thought to be difficult to form the insulation film and the support member using the same material in the same process because the thicknesses thereof are considerably different. Accordingly, the manufacturing process of the device has been complicated, the cost thereof has been raised, and so on.